I. Field of the Invention
This invention relates to packages, and more particularly, to a substrate wafer package with replaceable resilient cushions between which the wafers are suspended to prevent sliding or pivoting of the wafers on the edge profile, thus eliminating particle generation and damage to the wafers.
II. Description of the Prior Art
A variety of packages for holding and transferring substrate wafers are known in the prior art. For example, U.S. Pat. No. 5,046,615 to Nentl discloses a disc shipper device utilizing downwardly extending dentate leaves or resilient flanges in a row of crenate scallops in the cover to maintain the wafers or discs in an up-right parallel spaced part alignment and provide secure positioning of the discs to prevent transverse or lateral motion within the last shipper.
U.S. Pat. No. 4,966,284 to Gregorson et al., discloses a substrate package container for storing and transporting substrate wafers. The container disclosed in this patent includes opposing rows of articulated cantilevered horizontal arms with centered V-grooves on each end for engaging the wafer.
U.S. Pat. No. 4,793,488 to Mortensen discloses a two part package for storing and transporting semiconductor wafers. This package contains a plurality of wafer contactors which exert a spring pressure against the wafers to secure the wafers in place.
U.S. Pat. No. 4,653,636 to Armstrong discloses a high temperature wafer boat. This wafer boat contains conventional ribs and a bottom supporting rib, side supporting rails and side retaining rails. These rails have aligned grooves to maintain the positioning of the wafers.
U.S. Pat. No. 4,588,086 to Koez discloses a two-part substrate carrier having a transparent lid. The base portion contains semicircular V-shaped grooves. The cover also includes V-shaped grooves for engaging the top of the wafer.
The Voss et al. U.S. Pat. No. 4,555,024 discloses a packaging unit for semiconductor wafers which contains spring tongues in the base to support surfaces and inwardly projecting retention cones in the lid. The wafers are fixed at only four contact points. The goal of this design is to maintain minimal contact with the wafer.
U.S. Pat. No. 4,450,960 to Johnson discloses a package which is contoured and contains flexible fingers which space and secure the wafers and provides an upward pressure towards the package top with respect to the package bottom.
U.S. Pat. No. 4,160,504 to Kudlich describes a package having a plurality of parallel, laterally extending guide ribs formed opposite each other and a plurality of knobs which cooperate to maintain the discs in an upright position.
U.S. Pat. No. 4,043,451 to Johnson discloses still another shipping container for semiconductor wafers. The lid has interior wafer locating ribs and resilient, curved wafer supports beneath and over the edges of the wafer. The base contains an elongated panel of soft springy plastic with a corrugated wafer engaging face.
While significant improvements in wafer package technology are set forth in the prior art references discussed above, real problems continue to exist even with the use of these prior art packages. Many of these problems arise given the nature of the wafer substrates which they are designed to contain. Such substrate wafers are easily breakable, easily scratched, and are therefore very fragile. They are easily damaged by particles or other environmental contamination. Certain other prior art packages described above can protect the wafers from the external environment. However, when such packages are used, the wafers have become damaged due to the packaging itself and from the internal environment of the package which becomes contaminated by particles which are generated as the wafers pivot, slide or rotate on their edge profiles in the package. Such internal contamination becomes more prevalent as the thermoplastics used to cushion or retain the substrate wafers in the package lose their elastic memory so that the wafers are no longer securely held. When such flexural creep occurs, the packaged wafers can pivot or slide on their edge profiles generating particles which can damage or contaminate the wafer substrates. Thus, these packages cannot only damage the edges of the substrate wafers, but also the highly sensitive face surfaces used in the manufacturing of intragrated circuits.
The present invention overcomes the disadvantages of the prior art by providing a ridged transparent, thermoplastic package having a base and a cover. Located within the cover is a cushion made from an elastomeric or flexible thermoplastic material. An identical elastomeric or flexible thermoplastic cushion is associated with the base so that when the package is used, the substrate wafers are sandwiched between the elastomeric cushions and firmly held in place by them. The two cushions have an identical structure. Each has a base comprising a pair of parallel rails. Extending between the parallel rails are a plurality of wafer engaging member. Each wafer engaging member is resilient, yet deformable, to securely engage the edge of the wafer. Each also has angled surfaces extending outwardly on either side. The edge of the wafer is, thus, firmly secured between the angled, outwardly extending surfaces. When the box is closed, the wafers are firmly held between the cushion on the base and the cushion in the cover in such a way that the possibility of damage to the wafer is greatly reduced as compared to the prior art packages discussed above.